1. Field of the Invention
This invention relates to meters for measuring energy. In particular, this invention relates to a system and method for compensating for potential and current transformers in meters for measuring energy.
2. Description of the Related Art
Electrical utility companies (“utilities”) track electric usage by customers by using power meters. These meters track the amount of power consumed at a particular location, such as a substation. The electric utility companies may use the power meter to charge its customers for their power consumption, i.e., revenue metering.
Traditionally, power meters used mechanical means to track the amount of consumed power. The inductive spinning disk power meter is still commonly used. The spinning disk drives mechanical counters that track the power consumption information.
Newer to the market are electronic power meters. Electronic meters have replaced the older mechanical meters, and utilize digital sampling of the voltage and current waveforms to generate power consumption information. In both, the mechanical and electronic power meters, when used with high voltages and currents, such as at a substation setting, the meters incorporate external sensors to divide the voltage and current into levels that are safe for the meters to read. Typically, a primary voltage is divided to a secondary 120 volt waveform, and a primary current is divided to a 5 amp secondary waveform. The sensors are current and/or voltage (potential) transformers, which introduce errors into the measurements in addition to errors introduced by other sources, such as the meters themselves. Furthermore, errors introduced by the current transformers are nonlinear throughout the range of magnitude of usage. Additionally, the current transformers are inductive by nature, and generate a phase shift which further degrades accuracy in measurements.
Therefore, it is an aspect of the invention to compensate for errors introduced by current and/or voltage transformers into readings by power meters.
It is further an aspect of the invention to compensate for nonlinear errors introduced by current transformers into readings by power meters.
Additionally, it is an aspect of the invention to compensate for errors introduced into readings by power meters due to phase shifts generated by the current transformers.